Devices for controlling the spatial distribution of the intensity of electromagnetic waves, such as light, are often designated as spatial light modulators (SLM's). Such devices which can be used in processing data are capable of spatially modulating a collimated coherent or incoherent beam of light with, for example, input data which is to be processed. The devices are appropriately coupled to optical data processing systems into which the data modulated light beam is supplied at a rate commensurate with the processing system's potential throughput, the optical processing system utilizing parallel processing without the limitations normally imposed by serial manipulation of the data.
Many different forms of spatial light modulators have been suggested by those in the art. A recent article, entitled "Spatial Light Modulators", by David Casasent and published in the Proceedings of the IEEE, Vol. 65, No. 1, January 1977, at pages 143-157, provides a summary of various types of spatial light modulators that have been suggested by the art. The devices described therein include SLM's using liquid crystal materials; materials which undergo surface deformation patterns (sometimes referred to as deformable SLM's), i.e., thermoplastic materials, dielectric oils, ruticon, or elastomers, or membranes combined with surface channel charged coupled devices (CCD's); alkali halide materials having intentionally introduced color center defects (sometimes referred to as photodichroic SLM's); materials which exhibit the Pockels effect (sometimes referred to as Pockels SLM's); materials using ferroelectric-photoconductor characteristics; materials using ferroelectric-photorefractive characteristics; and SLM's using acousto-optic techniques, magneto-optic techniques, techniques utilizing the characteristics of amorphous semiconductor materials; and techniques using magnetic-bubble devices.
In most cases, however, the above devices are only optically addressable by using a scanning light beam, for example, or electron beam addressable by using a scanning electron beam. Such devices are cumbersome and expensive to fabricate and are slow in operation. Of the relatively few types of devices which are electrically addressable, such as devices which use membranes deflected by electrical signals which are supplied through electrodes in contact with the membrane or devices which use membranes combined with charged coupled devices, the structure thereof is extremely difficult to fabricate and the membrane response is relatively slow so that such devices are not readily usable for high speed, real-time processing operations.
It is desirable, therefore, to devise spatial light modulators which can be fabricated with much less difficulty and at much less cost and which can operate at high speeds utilizing electrically or optically addressable input data.